I have also updated the tests to userequest.body* instead ofrequest.postData* except for the following:

• I changed the tests intests/page/network-post-data.spec.ts to be skipped for BiDi because these tests are mirrored by those intests/page/network-request-body.spec.ts
• I didn't changetests/page/page-request-fallback.spec.ts because it only tests overridden request bodies which are always available synchronously

Fixes the following tests in Firefox:

• tests/page/network-request-body.spec.ts:
  • "should return correct request body buffer for utf-8 body"
  • "should return request body w/o content-type"
  • "should throw on invalid JSON in post data"
  • "should return body for PUT requests"
  • "should get request body for file/blob"
  • "should get request body for navigator.sendBeacon api calls"
• tests/page/page-network-request.spec.ts:
  • "should parse the data if content-type is application/x-www-form-urlencoded"
  • "should parse the data if content-type is application/x-www-form-urlencoded; charset=UTF-8"
  • "should parse the json post data"
  • "should return multipart/form-data"
  • "should return postData"
  • "should work with binary post data"
  • "should work with binary post data and interception"
• tests/page/page-request-intercept.spec.ts:
  • "request.postData is not null when fetching FormData with a Blob"
  • "should intercept multipart/form-data request body"
• tests/page/page-route.spec.ts:
  • "should intercept when postData is more than 1MB"